Here is an excerpt on hemangiosarcoma in Golden Retrievers
PLOS ONE: Gene Expression Profiles of Sporadic Canine Hemangiosarcoma Are Uniquely Associated with Breed
Another good article. Interesting note in here that says a cancer "similar" in people is caused by chemical exposure. But if that is the case with hemangiosarcoma, why is it only prevalent in some dog breeds?
Hemangiosarcoma - CVM - ACCR, University of Minnesota